mlx4_core: Change command token on timeout

    
The FW command token is currently only updated on a command completion
event. This means that on command timeout, the same token will be
reused for new command, which results in a mess if the timed out
command *does* eventually complete.

This is the same change as the patch for mthca from Michael
S. Tsirkin <mst@dev.mellanox.co.il> that was just merged.  It seems
sensible to avoid gratuitous differences in FW command processing
between mthca and mlx4.

Signed-off-by: Roland Dreier <rolandd@cisco.com>